When under certain circumstances bone tissue is fractured or broken, it must be welded together again in order to recover its initial state. To that end there are many different devices which are used in the event of breaking due to trauma or accident, or in the event that bone tissue must be previously broken or fractured in the operating room in order to perform surgery.
The devices used to join bone fragments generally consist of clamps, the parallel ends of which are inserted into each of the bone fragments to be joined together. An example of this type of device is the one described in patent EP 1171050 B1, in which the two fragments of the sternum that must be joined together after a surgical operation on the chest (cardiovascular, pulmonary . . . ) are fixed by the action of a C-shaped clamp with a center piece from which ends opposite to one another originate, said clamp provided with a loop in the area of the center piece which is deformed when cooled to be able to apply the ends to the bone fragments of the sternum and which, once applied on the bone mass, returns to its original shape when it reaches body temperature, comprising the mentioned ends and therefore the joining of the fragments.
Other clamp-shaped devices are described, each having its own particularities, in patent documents U.S. Pat. No. 5,449,359, U.S. Pat. No. 5,788,698, U.S. Pat. No. 4,456,006 and U.S. Pat. No. 484,328.
Alternatively, surgical connectors can also be used to join bone fragments such as the connector described in U.S. Pat. No. 5,743,913 A1, in which a slightly curved plate provided with multiple openings and nodes homogenously distributed therethrough comprises at least three also slightly curved extensions or ribs joined to at least three of these nodes and suitable for receiving fastening means, such as screws.
All these devices involve the drawback that they are difficult to apply, requiring the use of applicator devices and/or additional instruments that are also very complex, or requiring additional elements for securing them in the bone fragments that must be joined together.
In the same manner, devices are widely used in the field of neurosurgical operations for the fixation of flaps or bone fragments which are generally provided with means for the fastening of the flaps, and suitable for being supported on or containing the cranial bone mass in a space reserved for such purpose, or by incision by means of a sharp element in said cranial mass. These devices are placed between the flap and the cranial bone, and except in the event that they are made of a biodegradable or absorbable material, they are permanently placed in the cranium.
One of the existing and widely used types of flap fixation devices generically consists of a device with two considerably circular elements facing one another in the form of semi-spherical caps joined by means of a shaft or shank through which the semi-spherical elements can be moved closer to one another in order to adjust the device to the cranium and flap bone mass thickness. Once the mentioned device is adjusted, both the flap and the cranial bone mass are supported between the semi-spherical elements, forming the bearing and supporting means of the flap and of the cranium. In this type of device, the neurosurgeon cuts the excess remaining shank once it is well placed between bone masses.
Patent document EP 1477122 A2 describes a device such as those described in the preceding paragraph consisting of an implant for adjacent cranial bone fragment fixation, comprising two fastening elements, an end element and an inner element, which by means of a joining element, which is wire, that is adjustable and can be led through the external fastening element, causes the sliding of the inner fastening element, which comes close to the external fastening element, said wire being led through multiple openings made in the fastening elements. The device described in EP1477122 A2 comprises additional joining means between the internal and external fastening elements, such as shafts perpendicular to the mentioned internal and external fastening elements, which can consist of ratchet teeth systems, clips or fragments with a trapezium- or triangular-shaped longitudinal section with side-projecting tips.
Patent document WO00/49949 likewise describes a fixation system comprising a fastening element of biocompatible material consisting of a disk-shaped head and a shank, in which said shank has a surface having ratchet teeth thereon, said fastening element consisting of a second, also disk-shaped, closure element, provided with an opening through which the shank can be inserted for the purpose of bringing the two disk-shaped elements together until the upper and lower edges of the bone fragments to be joined together.
These types of devices such as those described in patent document WO00/49949 are difficult to manufacture and store because of their size and because of the fact that they consist of an element from the central part of which there extends a shaft that is integral and perpendicular to the plane defined by the same, and they are subjected to a more demanding load state since the load is concentrated in the joint between the shaft and the disk-shaped head, whereby existing a higher probability of failure, especially when it is made with non-metallic materials.
Furthermore, many of these devices comprising two plates or elements joined by a rigid shaft involve the drawback that their entire surface does not adapt to different thicknesses and irregularities of the cranium and/or flap, resulting from the actual anatomy of this party of the body.
Most of these devices, specially designed to join bone flaps to the cranial bone mass, must be applied with the use of complex instruments, such as applicators suitable for engaging the shaft or shank joining the disk-shaped elements; and provided with means of pushing one of said disks, which is moved over the mentioned shaft in order to be close to its homologue.
The object of this invention provides novel solutions to the problems of manufacture, storage, resistance, adaptation to bone thicknesses and placement of bone fragment particularly bone flap, fixation devices. It is furthermore easy to apply due to simple elements provided in the actual fixation device and allows the possibility of being adjusted without the need for additional instruments.